1. Field of the Invention
The present invention relates to a steplessly adjustable, belt-driven conical-pulley transmission having two pairs of input-side conical disks and two pairs of output-side conical disks that are drivingly connected together by two endless torque-transmitting means connected in parallel.
2. Description of the Related Art
Conventional steplessly adjustable, belt-driven conical-pulley transmissions often have a complicated adjustment mechanism that additionally requires a relatively large space. Depending upon the size of the available drive assembly, problems can arise with the available installation space.
It is therefore an object of the present invention to provide a steplessly adjustable, belt-driven conical-pulley transmission having two pairs of input-side conical disks and two pairs of output-side conical disks that are drivingly connected together by two endless torque-transmitting means connected in parallel, and that is quickly and reliably adjustable and is optimized with respect to the required installation space.
The object is achieved by providing an asymmetrical conical-angle arrangement in a steplessly adjustable, belt-driven conical-pulley transmission having two pairs of input-side conical disks and two pairs of output-side conical disks that are drivingly connected together by two endless torque-transmitting means connected in parallel. The asymmetrical conical-angle arrangement has proven to be extremely advantageous in reference to the adjustment of the distance between the conical disks.
A preferred embodiment of a belt-driven conical-pulley transmission is characterized in that the two pairs of input-side conical disks and the two pairs of output-side conical disks in each case include two outer, axially-fixed conical disks. Preferably, the inner conical disks are designed to be axially displaceable. That arrangement leads to an advantageous uniform contact pressure on both of the endless torque-transmitting means, and thereby to an equal load division.
An additional preferred embodiment of the belt-driven conical-pulley transmission is characterized in that the outer, axially-fixed conical disks have a small cone angle, particularly a maximum of about 1°. The skew of the endless torque-transmitting means can be kept as small as possible due to the small angle of the axially-fixed conical disks. Ideally the angle would be 0°.
Another preferred embodiment of the belt-driven conical-pulley transmission is characterized in that between the outer, axially-fixed conical disks two axially-displaceable conical disks are arranged that have a relatively large cone angle, particularly between 10° and 30°, preferably between about 15° and 20°, and especially about 17°. The relatively large cone angle of the axially-displaceable conical disks results in a relatively long guide pathway along the inner surface of the conical disks. The distribution of the overall cone angle in the above-described way between the axially-fixed and the axially-displaceable conical disks leads to a shorter, more compact structure.
A further preferred embodiment of the belt-driven conical-pulley transmission is characterized in that two actuators, particularly two piston/cylinder units, are provided between the axially-displaceable conical disks. The two actuators, which can be in the form of hydraulic cylinders, for example, serve to provide the necessary contact forces as well as the adjustment forces. The double piston principle has proven particularly advantageous in combination with the centrally-located, axially-displaceable conical disks. The central location of the contact pressure cylinders leads to an equal contact pressure on the two endless torque-transmitting means and therefore to an equal load division.
A further preferred embodiment of the belt-driven conical-pulley transmission is characterized in that the two axially-displaceable conical disks are guided relative to each other in the axial direction. By reason of the guide arrangement a tilting of the two conical disks relative to each other is prevented.
Another preferred embodiment of the belt-driven conical-pulley transmission is characterized in that the two axially-displaceable conical disks are non-rotatably connected together by a form-locking connection, particularly by a gear-tooth arrangement. In that way, it is ensured that the torque will be securely transmitted from the input shaft to the output shaft.
An additional preferred embodiment of the belt-driven conical-pulley transmission is characterized in that between the axially-displaceable conical disks several centrifugal weights and a transmission disk are arranged. The disk includes spiral grooves for converting radially outward movements of the centrifugal weights into a rotational movement of the transmission disk. A screw thread on the inner diameter of the transmission disk serves to convert the rotational movement of the transmission disk into an axial movement of the axially-displaceable conical disks relative to each other. Thereby, a reliable, mechanical compensation for the centrifugally-generated oil pressure is produced. The centrifugal weights are equally circumferentially distributed relative to the associated conical disks. Preferably, the centrifugal weights are provided with pins that axially engage the grooves of the transmission disk. The centrifugal weights are preferably supported on the opposite side by straight, radial grooves in the associated coupling disc. Preferably a coarse screw thread is provided on the inner diameter of the transmission disk. The mechanical compensation arrangement for centrifugally-generated oil pressure causes the two axially-displaceable coupling disks to be pulled together against the centrifugally-generated oil pressure, and that mechanical arrangement thereby compensates for it. The mechanical compensation arrangement for centrifugally-generated oil pressure can also be used advantageously in connection with a symmetrical cone angle design.
The object indicated above is achieved in a continuously variable belt-driven conical-pulley transmission having two pairs of input-side and two pairs of output-side conical disks that are drivingly connected together by two parallel, endless torque-transmitting means and that have symmetrical cone angles, in that the two pairs of input-side and the two pairs of output-side conical disks each have only one axially-fixed conical disk. That results in the advantage that the negative effects of an asymmetrical cone angle arrangement can be circumvented.
A preferred embodiment of the belt-driven conical-pulley transmission is characterized in that both middle conical disks of the input-side conical disk pair are connected together as one piece. The contact pressure advantageously then takes place from the side where the axially-displaceable conical disk is located.
An additional preferred embodiment of the belt-driven conical-pulley transmission is characterized in that two of the three axially-displaceable output-side conical disks are coupled together in the axial direction. The coupling can be achieved, for example, by inner threaded rods.
Another preferred embodiment of the belt-driven conical-pulley transmission is characterized in that the two axially-displaceable output-side conical disks are coupled together by threaded bushings. A secure support of the axially-displaceable conical disks against each other can be assured by the threaded bushings.
A further preferred embodiment of the belt-driven conical-pulley transmission is characterized in that the space between the two axially-displaceable output-side conical disks is radially outwardly sealed by a telescoping cylinder. That contributes to keeping small the dimensions of the belt-driven conical-pulley transmission in accordance with the invention.
The above-mentioned object is also achieved in a steplessly adjustable, belt-driven conical-pulley transmission having two pairs of input-side and two pairs of output-side conical disks that are drivingly connected together by two endless torque-transmitting means connected in parallel, in which between two conical disks that operate together with different endless torque-transmitting means, on one of the conical disks several threaded spindles distributed in a star pattern in the radial direction are rotatably supported, on each of which a centrifugal weight is movably guided and which is coupled with a toothed rack in such a way that rotational movement of the threaded spindles, which is caused by a movement of the corresponding centrifugal weight in a radial direction, is transformed into an axial displacement of the corresponding toothed rack that is coupled with the other conical disk. Thereby, a reliable device is provided to compensate for the centrifugally generated oil pressure.
The above-mentioned object is also achieved in a steplessly adjustable, belt-driven conical-pulley transmission having two pairs of input-side and two pairs of output-side conical disks that are drivingly connected together by two endless torque-transmitting means connected in parallel, two conical disks that operate together with different endless torque-transmitting means are coupled with one another by a toggle link device on which at least one centrifugal weight is installed and in such a way that the two conical disks move toward each other when the centrifugal weight moves radially outward. Thereby a further reliable device is provided to compensate for the centrifugally-generated oil pressure.
The above-mentioned object is achieved in a drive unit, especially for motor vehicles, by the inclusion of the above-described transmission.